CVE-2023-27351

PaperCut NG/MF: Improper Authentication

As of , CVE-2023-27351 in PaperCut NG/MF is on CISA's list of exploited vulnerabilities: CISA listed it on . Our patch-first group: Patch now.

Exploited
Yes: CISA listed it on 20 April 2026
US federal deadline
4 May 202614 days after CISA listed it. US federal civilian agencies must fix it by then.
Used in ransomware campaigns
KnownCISA changed it from Unknown to Known on 21 April 2026.
EPSS score
0.78Higher than 99% of the CVEs EPSS scores. EPSS estimates the chance of exploitation activity in the next 30 days.
Public exploit
None foundNeither Metasploit nor Exploit-DB lists one.
Fix
Vendor advice: www.papercut.comLinks below, from CISA's entry.

What CISA says to do

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

CISA's required action

What the flaw is

PaperCut NG/MF contains an improper authentication vulnerability that could allow remote attackers to bypass authentication on affected installations via the SecurityRequestFilter class.

CISA's description

This vulnerability allows remote attackers to bypass authentication on affected installations of PaperCut NG 22.0.5 (Build 63914). Authentication is not required to exploit this vulnerability. The specific flaw exists within the SecurityRequestFilter class. The issue results from improper implementation of the authentication algorithm. An attacker can leverage this vulnerability to bypass authentication on the system. Was ZDI-CAN-19226.

The CVE record's description, from zdi

CVE published
20 April 2023
Assigned by
zdi
CVSS
8.2 High (CVSS 3.0, from the CNA)
CWE-287
Improper Authentication
CISA SSVC, exploitation
active
CISA SSVC, automatable
yes
CISA SSVC, technical impact
total

Timeline

  1. The CVE record was published.
  2. CISA added it to its list of exploited vulnerabilities.
  3. CISA changed its entry. Ransomware use: Unknown to Known.
  4. The US federal deadline to fix it.

NG/MF: other exploited entries

VulnerabilityProductOur groupListedDeadlineEPSS
CVE-2026-81578Missing Authentication for Critical FunctionPaperCut NG/MFPatch this weekMetasploit module; EPSS 0.850.85
CVE-2026-82078Unsafe ReflectionPaperCut NG/MFPatch this weekMetasploit module; EPSS 0.610.61
CVE-2023-2533Cross-Site Request Forgery (CSRF)PaperCut NG/MFPatch soon0.29

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